Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
TAPERED BRUSH BRISTLES WITH CLAY OR
SILICA ADDITIVE AND BRUSHES MADE THEREFROM
FIELD OF THE INVENTION
The present invention relates to textured tapered filaments. Particularly,
the invention relates to tapered filaments of thermoplastic polymer having a
clay
or silica additive to increase the surface of the filament and improve pickup
and
release performance of coatings when used in a brush application.
BACKGROUND OF THE INVENTION
Synthetic filaments produced from thermoplastic polymers have long been
used as an alternative for natural bristles such as hog hair in the
manufacture of
paintbrushes. These thermoplastic polymers provide advantages over natural
bristles in cost, consistency of quality, and performance, especially in modem
day
paintbrushes as painting has transitioned from solvent based to water based.
The
thermoplastic filaments are often tapered to provide a large diameter end
(butt)
which is contained within the ferrule of the brush while providing a smaller
diameter end (tip) at the end of the paintbrush.
The synthetic filaments can be produced from a wide variety of
thermoplastic polymers including polyamides, polyesters (US Pat. No.
3,706,111),
and polyolefins, in a wide variety of configurations including solid and
hollow,
and in a wide variety of cross-sections, including circular, oval, trilocular,
tetralocular, lobate (US Pat. Nos. 4,279,053 and 4376,746, Can. Pat. No.
1,007,032), or may contain multiple voids. Much work has been done in the
trade
to improve paint pickup and paint release of paintbrushes by experimenting
with
blends of different polymers, configurations, and cross-sections. However,
with
all the inventions in these areas introduced to the trade in the past, the
highest
quality, best performing, professional brushes of today are still produced
from
tapered solid round filaments of nylon 6,12 (specifically filaments sold under
the
trademark TYNEX filaments by E. I. du Pont de Nemours and Company)
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blended with tapered solid round filaments of polybutylene terephthalate
(specifically filaments sold under the trademark OREL., filaments by E. I. du
Pont de Nemours and Company).
US Pat. No. 5,032,456 teaches a microcellular filament to better simulate
the surface of natural hog bristle for paint application. This filament has a
porous
surface to improve paint pickup and hold, but does not show any improvement in
paint release. Also, because of these pores on the surface, brushes made with
these filaments can be hard to clean, and as a result, these filaments are not
used in
premium professional brushes today. In US Pat. No. 5,128,208, improved paint
pickup in oil paints is accomplished by a filament that is easily flagged.
However,
this filament is not preferred because it is difficult to tip without flagging
and does
not provide any improvement in paint release, especially of water based
paints.
US Pat. No. 4,279,053 discloses trilocular and tetralocular filaments to
provide
improved flagging and lower filament densities. Although the improved flagging
accomplished with these filaments can improve the paint pickup of the brush,
the
trilocular filaments do not have the required stiffness and bend recovery that
allow
for use in premium professional brushes.
Significant work has been done in the past to add clay or silica of various
sizes and of various amounts to nylon and polyester filaments and fibers to
improve physical properties such as strength, fracture toughness, or
abrasiveness.
E. I. du Pont de Nemours and Company sells an abrasive filament, marketed
under
trade name TYNEX A, which contains aluminum silicate, but is not tapered, and
is not used in or recommended for use in paintbrushes. US Pat. No. 5,727,106
discloses the addition of clay to nylon and polyester level (non-tapered)
filaments
as a polishing agent for use in toothbrushes. But the disclosure does not
consider
pickup and release properties or the use of clay additives for tapered
filaments for
use in coating applications. Clay or silica has also been added to filaments
and
fibers to better imitate natural bristles in surface appearance and feel, but
no work
has been done where clay was added to tapered filaments for use in
paintbrushes
or other coating application uses. Furthermore, no tapered filament has shown
the
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maa-nitude of improvement in paint pickup and release and paint stripe length
as
the filament of this invention.
SUMMARY OF THE INVENTION
The present invention provides an improved polymeric tapered brush
bristle produced with 0.1 ro to 10% clay or silica additive by weight of the
total
composition. The clay additive modifies the surface of the filament and
improves
the pickup and release performance of coating on the bristle when used for
application of coating such as in a paintbrush, mascara brush, nail polish
brush qr
cosmetic brush.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. I is an illustration of one brush bristle oaf the prior art.
Fig. 2 is an illustration of one brush bristle of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The filaments of the present invention are prepared by equipment that is
traditionally used for extruding, stretching and tapering, filaments in the
manufacture of solid, tapered thermoplastic bristles. To produce tapered
filament,
the filament is drawn as described, for example, in U.S. Pat. No. 2,418,492 .
Thermoplastic polymer resin pellets are blended with the clay or silica
additive. The blended resin is then fed to an extruder which melts the
thermoplastic resin and transports the melted polymer. The clay is added at a
loading ratio of from 0.1 % to 10% by weight of the total composition.
Loaciing
below 0.1 % by weight of the total composition does not achieve the desired
performance characteristics. Loading above 10% may result in a less than
optimum extrusion process, such as the breaking of filaments or difficulty
drawing
the filaments. The particularly preferred embodiment of a filament of the
present
invention contains about 5% by weight of the total composition of the clay or
silica additive.
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The melted polymer :s extruded through a spinneret to form f lament
strands. The strands are quenched for solidification in a cooling bath.
typically
filled with water. The flanients are then drawn in accordance ~N-ith a
repetitive
schedule of linear rates comprising a period of acceieration and deceleration.
and a
period of unifon-n withdrawal. In aeneral, such filaments are tapered to
produce a
tip diameter that is about from 0.5 to 0.75 tinies the diameter of the butt
diameter.
Each filament is then oriented. stretched between two roll sets by running the
second roll set faster than the first roll set, to improve lonQitudinal
strenath of the
filament. The oriented filament may then be heated to induce partial
crystallization rendering good bend recovery. The heat setting is typically
carried
out in a gas such as by blowinc, hot air over the filament for about 30 to 90
seconds, or in a liquid bath such as by passing the filament through a bath of
oil
for about 2 to 10 seconds.
The filaments are then cut at each point of minimum diameter and
gathered as bundles of product. Each bundle is a-ain cut at the center arid
the
ends are trimmed to produce two bundles suitable for further processing into
brushes. The individual bristles may be tipped and flageed by conventional
procedures as described, for example, in U.S. Pat. Nos. 2,697,009 and 2,91
1,761.
The bristles are then fabricated into brushes
using techniques well known in the art.
The filaments of the present invention can be prepared from a wide variety
of therrnoplastic polymers including, polyamides, polyesters and polyolefins,
styrenes, fluoropolymers, polyvinylchloride, polyurethane, polyvinylidene
chloride, polystyrene and styrene copolymers, and any combination thereof.
Polvamides preferred in brush manufacturing include nylon 6, nylon 11, nylon
6.6,
nylon 6,10 nylon 10,10, and nylon 6,12. Nylon 6,12 is particularly preferred
for
paintbrush, mascara brush, nail polish brush and cosmetic brush applications.
The
filaments of the present invention when produced with nylon 6,12 have a flex
modulus of 430 to 630 ksi, a tensile strength of 37 to 80 ksi, a breakload of
0.80 to
12 lb, an elongation of 20 to 50% and bend recovery of 90 to 100%.
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Polyesters that have been found particularly well suited for bristle
manufacture include polybutylene terephthalate and polyethylene terephthalate
and blends thereof. Of the many polyolefins which can be used for bristle
manufacture, polypropylene is preferred. The filaments may also be prepared by
a coextrusion of one or more polymers to form a coaxial structure, a
concentric
structure or other configuration.
Preferred clay and silica additives of the present invention have a particle
size of between 0.01 m to 100 m. Many types of additives may be used
including, but not limited to, paint particles, rubber particles, aragonite
clay,
calcium carbonate, orthorhombic clays, calcite clay, rhombohedral clay, kaolin
clay, bentonite clay, dicalcium phosphate, tricalcium phosphate, calcium
pyrophosphate, isoluble sodium metaphosphate, precipitated calcium carbonate,
magnesium orthophosphate, trimagnesium phosphate, alumina, hydrated silica
xerogel, metal aluminosilicate complexes, sodium aluminum silicates, zirconium
silicate, silicon dioxide, silicon carbide. The clays may be either hydrous or
anhydrous and with or without surface modifiers. Examples include, but are not
limited to, Hydrite UF, Hydrite 121-S and Hydrite Flat D, manufactured by the
Dry Branch Kaolin Co. of Dry Branch, Georgia; and Burgess 2211, manufactured
by Burgess Pigment Co. of Sandersville, Georgia.
The clay or silica additive modifies the surface of the bristle, thus reducing
the surface friction between bristles, which improves the coating performance
when used in a brush application. Coating pickup, paint release, and paint
stripe
length are increased significantly. Figure 2 illustrates the modified surface
of the
bristle of the present invention as compared to the surface of the bristle of
the
prior art illustrated in Figure 1.
The brush bristles of the present invention have tip diameters of 0.003 in
to 0.015 in and butt diameters from 0.005 in to 0.020 in. The brush bristles
may
be of any length and are limited only by their use in a particular
application. For
the paintbrush application, the preferred length of the bristles is between
2.00 in
and 5.00 in, the butt diameter is preferably between 0.007 in and 0.015 in,
and the
tip diameter is preferably between 0.004 in and 0.010 in. In a particularly
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preferred embodiment of the mascara brush, the preferred length of the bnstles
is
between 0.50 in and 2.00 in having a preferred butt diameter of 0.005 to 0.010
in
and tip diameter of 0.003 to 0.005 in. For other applications, the preferred
thickness of the bristles is selected to provide a level of functionality for
the
individual application.
The bristles of the present invention may be of different cross-sectional
shapes, which are produced by extrudina through different capillary shapes
within
the spinneret plate of the spinneret. Depending on the desired application of
the
bristles, using conventional techniques known in the art, each filament
produced
can be straight, curved, looped or arched. The bristles of the present
invention can
be produced in any color by blending the polymer with different colorants or
by
other coloring techniques known in the art. Also, the bristles can be easily
tipped,
flagged, or processed in the same manner as standard solid round tapered
filaments.
The present invention is further illustrated by the following specific and
comparative examples.
Example I
Nylon 6,12 polymer resin (commercially available under the product name
ZYTELO from E. I. du Pont de Nemours and Company of Wilmington, Delaware)
was blended with 10% by weight of the total composition of clay concentrate
(commercially available from Chroma Corp. of McHenry, Illinois). The clay
concentrate consisted of 50% by weight of Burgess 2211 clay in ZYTELO 6,12
nylon resin, (manufactured by Burgess Pigment Co. of Sandersville, Georgia).
The nylon and clay concentrate blend was gravity fed to the extruder.
A 120 hole spinneret plate with 0.031-inch diameter round capillaries was
installed into the spinneret and the polymer was extruded at 240 C and
quenched
in 25 C water located approximately 1.0 in below the spinneret plate. The
resulting filaments contained 5% by weight of the Burgess 2211 clay. The
resulting filaments were tapered using rubber pinch rolls which were operated
at a
cyclically varying surface speed as described in U.S. Pat. No. 2,418,492 which
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resulted in a correspondingly varying strand caliper fronl 0.016 to 0.024 in.
The
tapered filaments were oriented by a draw ratio of 3.75:1 to obtain varying
strand
diameters of 0.008 to 0.012 in. The filaments were heat set by passing through
a
170 C - 180 C oven. After spinning, drawing, and heat setting, the filaments
were cut at each point of minimum diameter and gathered as bundles of product.
Rubber bands were placed on the bundles and each 2.0-inch diameter bundle was
again cut at the center and ends trimmed to produce two bundles suitable for
further processing into paintbrushes. The two bristle bundles produced were of
a
solid round diameter and measured 3.50 in and 3.75 in in length.
The bristle bundles were then fabricated into two three-inch wall
paintbrushes using commercial manufacturing techniques. Brush I was composed
of 100% of the nylon filaments of the present invention. Brush 2 was composed
of a blend of the nylon filaments of the present invention and of commercially
available solid round polyester filaments. Brush I and Brush 2 were evaluated
for
paint performance and compared to three of the best commercially available
professional brushes, Brush 3, Brush 4, and Brush 5, all composed of a blend
of
commercially available solid round nylon and polyester filaments of different
sizes and lengths.
The brushes were evaluated by the procedure described in DuPont
Filaments Marketing Publication, "Paintbrush Evaluation Test." The "Paintbrush
Evaluation Test" measures a paintbrush's ability to pick up paint, to release
the
paint (lay paint down on a surface), and to visually show how effectively this
is
done. These key results are measured by the "Paint Pickup", "Paint Laydown"
and "Stripe Length" measurements. The Paint Stripe test simulates a painter
painting a horizontal stripe on a vertical wall. A special black lacquered
paper is
used for the paint stripe test. The Stripe Length is the actual measurement on
the
paint stripe from the beginning of the stripe to the point where the brush
begins to
skip. Although this skip point is somewhat subjective, as long as all the
stripes
are judged on the same basis, the comparative results will be consistent. The
procedure to measure the three test criteria includes the following steps:
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(1) Weigh the clamp and brush, including handle, and record the "Clamp-Brush"
weight.
(2) Dip the brush for 30 seconds into the paint to a predetermined length of
the
bristle then let the paint drip for 30 seconds.
(3) Weigh the clamp and brush with the paint and record the "Before" weight.
(4) Paint one left to right stripe with the dipped brush without letting the
brush
paint a return stripe.
(5) Quickly reweigh the clamp and brush and record the "After" weight.
(6) Calculate the Paint Pickup by subtracting the "Clamp-Brush" weight from
the
"Before" weight.
(7) Calculate the Paint Laydown by subtracting the "After" wei-ht from the
"Before" weight.
(8) Once the paint is dry, measure the length of the stripe from -here the
paint
begins to where the brush begins to skip. This measurement is the "Stripe
Length." '
Results of the test are shown in Table 1. The results demonstrate a
significant improvement in paint performance of the brushes of the present
invention (Brushes 1 and 2) when compared to the best brushes available today
(Brushes 3, 4 and 5).
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Table 1: Paint Performance
Brush Paint Paint Paint Stripe
Pickup (g) Lavdo~~,n (g) Length (in.)
Brush 1 37 4.3 18.00
Brush 2 32 5.2 23.50
Brush 3 21 3.3 14.75
Brush 4 25.3 3.2 14.25
Brush 5 25.4 3.5 14.00
Brush 6 32.9 6.1 20.00
Brush 7 32.4 4.6 13.75
The performance results of Brush 1 and Brush 2 for paint pickup and paint
laydown were compared to the results of Brush 5 since Brush 5 achieved the
best
result for these tests. The performance results for paint stripe length were
compared to the results of Brush 3 since Brush 3 achieved the best result for
that
test. Brush 1 showed a 46% improvement in paint pickup, a 23% improvement in
paint laydown, and a 22% improvement in paint stripe length. Brush 2 showed a
26% improvement in paint pickup, a 49% improvement in paint laydown and a
60% improvement in paint stripe length. These results show that the filaments
of
the present invention, especially when blended with polyester filaments in a
brush,
achieve a significantly better coating performance than standard nylon and
polyester filaments.
Example 2
The filaments of Example 2 were produced using the same process as
described in Example 1 above. Filaments were produced having lengths or 3.00
in, 3.25 in, 3.50 in, and 3.75 in. A second set of filaments was produced
using a
180 hole spinneret plate with 0.026-inch diameter capillaries. The resulting
extruded filaments had varying diameters of 0.010 to 0.018 in. These were
drawn
at a ratio of 3.75:1 and heat set to produce filaments with varying diameters
of
0.005 to 0.009 in. The resulting filaments were cut to lengths of 3.25 in and
3.50
in. These 6 products were assembled into a three-inch wall brush, Brush 6,
using
a commercial manufacturing process.
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Brush 6 was evaluated using the DuPont Filaments "Paintbrush
Evaluation Test" described in Example 1. As in Example 1, the performance
results for paint pickup and paint laydown of Brush 6 were compared to the
results
of Brush 5 since Brush 5 achieved the best result for these tests. The
performance
result for paint stripe length was compared to the results of Brush 3 since
Brush 3
achieved the best result for that test. Results for Brush 6 are shown in Table
1.
Again, significant improvement was demonstrated using the filaments of the
present invention achieving a 30% improvement in paint pickup, a 32%
improvement in paint release, and a 36% improvement in paint stripe length.
Example 3
Using the same process as described in Example 1, filaments were
prepared from a blend of ZYTEL 6,12 nylon and 2.5% of the clay concentrate,
resulting in a bristle containing 1.25% by weight of clay additive. The
filament
was cut to a length of 3.75 in and assembled into a three-inch wall
paintbrush,
Brush 7, using a commercial manufacturing process. The brush was evaluated
using the DuPont Filaments "Paintbrush Evaluation Test" and compared to the
results of Brush 5 and Brush 3 as described in Example 1. Results are shown in
Table 1 for Brush 7. Although produced with one size of filaments of the
present
invention, Brush 7 still showed a 28% increase in paint pickup, a 31 %
improvement in paint laydown, and almost an equivalent performance in paint
stripe length (93% of Brush 3's paint stripe length).
Although the invention has been described with reference to several
particular embodiments, it will be understood to those skilled in the art that
the
invention is capable of a variety of alternative embodiments within the spirit
and
scope of the appended claims.
